i-phones transmitting on illegal channels
Last Post: December 2, 2010:
I just enabled channels 12 - 14 on my protocol analyzer, and found many Apple i-phones sending out Probe Requests on these three channels. These are supposedley un-modified units, sold here in the US.
Has anyone else seen this, and how are they getting away with it?
You need to check this with a spectrum analyzer. With channel overlap it is common to see a TX from channel 11 (or other channels for that matter) show up on other overlapping channels in a protocol analyzer.
I have seen that before, but when that happens the channel number in the frame doesn't match the channel number I'm scanning.
And the FCS's are also showing as correct.
I'll try it in the rf screen room with the spectrum analyzer!
In my experience the packet capture tool will display the channel it was on when it found the frame because very few frames actually transmit their intended channel. Probes don't have a field for channel number so the analyzer will only display the channel it was on when it heard the frame.
The FCS being correct is a good observation. If the analyzer was on channel 14 and the Tx was coming from channel 11 you would think that the FCS would have failed.